Electrophotographic copying apparatus

ABSTRACT

Disclosed is an electrophotographic copying apparatus comprising an improved optical system for reproducing an original image on a photoconductor, comprising a stationary lens, a linearly displaceable reflecting arrangement comprising at least two scanning reflectors joining each other in fixed angular relationship and at least one illuminating reflector rigidly connected to the scanning reflectors; and means for displacing the reflecting arrangement along a straight line in response to movement of the photoconductor.

United States Patent 91' 1 7 3,920,326 Hirth I 1 [451 Nov. 18,1975

'[75] Inventor: Heimo Hirth, Frankfurt am Main,

[541 ELECTROPHOTOGRAPHIC COPYING APPARATUS Primary Examiner-John M. l-loran J Attorney, Agent, or Firm-Richard L. Schwaab Germany 73 Assignee: Hoechst Aktiengesellschaft, v

' Frankfurt am Main, Germany g [57] v ABSTRACT Filed! 1974 v Disclosed is an electrophotographic copying apparatus [2] 1 App]; 524 comprising an improved optical system for reproduc- 5 ing an original image on a photoconductor, comprisg ing a stationary lens, a linearly displaceable reflecting [30] Foreign Application Prlority Data arrangement comprising at least two scanning reflec- Nov. 19, 1973 Germany 2357582 tors j g each other in fixed angular relationship and at least one illuminating reflector rigidly con- [52] us. Cl. 355/8; 355/66 ect t he ca ng efl c o a means for i [51] Int. Cl. G03G 15/28 pl cing the reflecting arrangement along a straight line [58] Field of Search 355/8, 66, 51, 65 in sp s to m m nt of the pho o ndu tor- [56] References Cited '30 Claims, 3 Drawing Figures UNITED STATES PATENTS 3,642,366 2/1972 Kawakubo 355/8 U S. Patent Nov. 18, 1975 Sheet 1 of3 3,920,326

. rwo a US. Patent Nov. 18, 1975 Sheet2of3 3,920,326

U.S. Patent Nov. 18, 1975 Sheet 3 of3 3,920,326

ELECTROPHOTOGRAPHICCbPYlNG I APPARATUS. I

BACKGROUND OF THE ruvjauriou I This invention relates to an felectrophotographic copying apparatus, and more especially to such an apparatus in which an original disposed on a planar fixed supporting surface is reproduced, strip by strip, on a moving charged photoconductive surface and which comprises moving optical components to assure that the image of the original is projected onto the moving photoconductor.

Copying apparatuses of this type are known, and several very different imaging systems for such devices have been suggested or have become known..For completeness, the most important of these systems suitable for electrophotographic apparatuses will be described in the following paragraphs.

In the simplest case, a stationary original is reproduced on a stationary photoconductor. In this case, exposure and reproduction do not offer any particular problems. Such devices are not suitable, however, for

high speed copying apparatuses.

A further system comprises a moving support plate for the original which is moved in synchronism with the photoconductor. In this case, the original is normally scanned strip-wise and reproduced on the photoconductorthrough an appropriate slot. Such systems have the serious drawback that the original must be displaced in the apparatus. This involves the risk of damaging the original, and in most cases an apparatus of this type can not be used for copying from books. Further, it is impossible with such devices to reproduce cut-outs from larger originals.

In a third group of imaging systems, a stationary original is reproduced on a moving photoconductor. One way of doing this is to make the exposure time so short that the lack of sharpness caused by the movement of the conductor is negligible. In these cases, a flash exposure is used. The difficulty with this type of apparatus is that the entire original must be reproduced on a planar photoconductor surface of corresponding size. For this purpose, the photoconductor web must be capable of rotation, which makes the apparatus relatively expensive.

A further class of reproduction system in which a stationary original is reproduced on a moving photoconductor may be characterized by the use of moving optical compensating elements. Two systems of this category have become particularly well known. For example, the system described in German Offenlegungsschrift No. 1,497,089 uses a swiveling mirror which is oscillated for scanning of the original. The original is placed on a cylindrically curved surface, with the axis of the cylinder and the swivel axis of the mirror coinciding. The swivel movement of the mirror is adjusted so that the strip of originalscanned is reproduced on the moving photoconductor as a stationary image. The main drawback of this apparatus is that the surface on which the original is placed must be curved. This is particularly undesirable because it renders it impossible to reproduce double pages of books on one and the same copy sheet.

In another apparatus, a movable mirror scanningoptical system is used. A system of this type is described, for example, in German Patent No. 1,215,503. This system comprises two groups of mirrors moved in the 2 same direction. The first group of mirrors comprises a scanning mirror which forms an angle of inclination of 45 with the supporting surface for the original and is moved along the supportingv surface at exactly the speed used for scanning. By means of the second group of mirrors which comprises two mirrors, the light beam already deflected by the first mirror is further deflected by 180. This second group of mirrors is moved at half the speed of scanning. The result achieved in this man'- ner is that the optical distance from each scanned area on the original to the lens or to the photoconductor remains constant. This apparatus has the serious drawback that two groups of mirrors must be providedv which must be moved in opposite directions. Despite the fact that the original is scanned at an angle of 90 and that the original is disposed on a planar surface, this drawback causes difficulties because the two groups of mirrors must be controlled by extremely accurate mechanical means, and this requires an extremely high mechanical expenditure.

In French Patent No. 1,503,632, for example, a further illuminating system with a movable mirror scanning optical system is described, in which only one mirror is moved. In this system, a mirror mounted at right angles to the supporting surface to be scanned is displaced. The beam arriving from the original and the beam extending beyond the mirror and reflected in the direction of the lens form an isosceles triangle with the supporting surface for the original This apparatus failed to find acceptance because in this case the original can not-be scanned at an angle of 90. Scanning is always done with a scanning angle of between about 30 and about 60. Thus, in order to produce an undistorted image with this system, the original must be reproduced with a corresponding angle on the photoconductor.

US Pat. No. 3,062,094 discloses a further apparatus comprisin a movable mirror system. In this apparatus, an optical system which is spaced respectively from the exposure slot of the photoconductor and from the original a distance corresponding in each case to twice the focal distance, is displaced along a straight line at half the speed of scanning. This principle, however, also involves some very annoying disadvantages. First of all, the space required is extremely large, because the distance between the moving lens and the stationary original is very long and must be provided within the apparatus. By means of mirrors, this space may be arranged so that it is no longer perpendicular; however, the large space required is still rather troublesome.

Another copying apparatus is described in Japanese Utility Model No. 6456/70, in which two mirrors, which are at right angles to each other and face the stationary original, are moved at a speed which corresponds to half the speed of the light-sensitive surface. The two mirrors face the original with their reflective surfaces so that the image of the original is twice reflected.

Although the last-mentioned copying apparatus possesses considerable advantages as compared with other prior art devices, the illumination of the original still causes technical difficulties. The Japanese Utility Model discloses a tubular light which is moved past the original at scanning speed, i.e., twice the speed of the mirrors. This requires a considerable equipment expenditure and involves the drawback that the lightsource must also be moved.

(SUMMARY OF THE INVENTION It is theefore' an object of the present invention to provide an improved electrophotographic copying apparatus.

'A further object of the invention is to provide an electrophotographic copying apparatus having an improved optical system for, reproducing an original image onto a photoconductor.. I

Still another object of the invention is to provide an improved optical system for use in an electrophotographic copying apparatus.

In accomplishing these objects, there is provided according to the present. invention, an electrophotographic copying apparatus which is characterized in that it comprises a combination of the following features: I

An electrophotographic copying apparatus, comprising (A) a photoconductive surface; (B) means for rotating the photoconductive surface, preferably about a closed path; (C) means for uniformly charging the photoconductive surface; (D) a slotted diaphragm arranged in front of the photoconductor and transversely to its direction of movement, through which the photoconductor surface is expo'sed;(E) a planar transparent support surface for an originalimage to be copied, either an original object or the virtual image of an original object; (F) optical means for reproducing the original image upon said photoconductive surface, this optical means comprising "(i) a first stationary lens for directing a scanned image from said original" image to said photoconductive surface, (ii) a reflecting arrangement adaptedfor displacement along a straight line,

this arrangementcomprising (a)' at least two scanning reflecting elements, preferably mirrors, rigidly joining with one another in fixed angular relationship, whereby, when the original image is scanned, a moving visual image is'produced behind the scanning reflecting element from the'view'point of said first stationary lens, and (b) at least'one illuminating reflecting element, preferably a mirror, rigidly connected to the scanning reflecting elements and arranged at such an angle to the original image supporting surface that a normal to the illuminating reflecting element, a normal to the original image, and'the straight line of displacement lie in a single plane, this straight line of displacement being defined such that the moving virtual image is displaced in a direction lying in the aforesaid plane when the reflecting arrangement is displaced along the line; a-

cumferential speed of the rotating photoconductive surface whereby the original image is scanned.

The problem which is actually solved by the present invention is the illumination of the original. The copying speed of an electrophotographic apparatus depends, to a certain degree, on the intensity of illuminascanned original orto the scanned virtual image of the original. Thenormal to the scanned original, to the illuproduces an exposure which is absolutely homogeneousg except for variations in thebrightness of the lamp. LThis results from the fact that the distancebetween the illuminated strip of the original and the light source is' always constant, because the illuminating mirror follows the movementofthe scanning mirrorsand the image of the light source on the original moves at exactly the same speed as the principal scanning point. The fixed mirror arrangement consistingof two scanning mirrors and at least one illuminating mirror is displaced along the line at such a speed that the component of speed parallel to the original or to its stationary virtual image corresponds exactly to half the circumferential speed of the photoconductor.

The construction of thecopying apparatus. according to the present invention is particularly simple and compact when the mirror arrangement comprises two scanning mirrors, which form a right angle between them and which are each inclined at an angle of 45 with respect to the transparent support plate for the original,

I and parallel to the original, or its virtual image.0n one tion in the plane of the original, the reproduction and scanning system, and the sensitivity of the photoconductor used. According to the present invention, at

least one illuminatingmirror is rigidly connected with side, the angled scanning mirror facing the support plate projects somewhat beyond the original tobe scanned. In this manner, the whole original may be scanned without any loss of information. As regards the quality of the reproduction, a angle mirror is insensitive to distortions about the junction of the mirrors. The illuminating mirror is arranged and/or behind the scanning mirror assembly in the direction of displacement, at a distance which at least slightly exceeds half the scanning length of the original.

An essential feature of the above defined electrophotographic copying apparatus is that only one mirror arrangement comprising fixedly connected scanning and illuminating mirrors is provided in the apparatus.

This mirror arrangement has the following functions:

l. To reproduce a stationary original on a moving photoconductor by optical compensation, and

2. To project a fixed light source in such a manner onto the stationary original that the projection of the light source on-the original moves synchroneously with the scanning when the mirrorarrangement is displaced.

It is to be understood, of course, that the functions of the mirrors may be executed in the same manner by appropriately ground prisms, but in the following only the term mirror will be used.

In the apparatus according to the invention, a displaceable mirror arrangement is used, the direction of displacement being so selected that the virtual image of the original formed-in the scanning mirrors is displaced only within this virtual imaging plane, but does not leave this plane. The virtual imaging plane is, so 'to speak, stationary. In principle, two mirrors are sufficient'for thisr'rianner of reproduction, but at least two mirrors are required. I

Since the areas of reflection generally move over the displaceable mirrors and since the scanning beams converge in the form of a trapezoid from the originalin the direction of the lens, the individual mirrors of the mirror arrangement may extend in the form of a trapezoid in the direction of the ray path, i.e., from the stationary support plate to the lens, with the angle of convergence corresponding approximately to the aperture angle of the lens utilized. In this manner, the mirror surfaces may be kept rather small, and accordingly, this construction is preferred.

The resulting oblique illumination of the original is very desirable, because it has been found that, in the case of a perpendicular scanning of originals, an oblique illumination at an angle of about 45 leads to optimum contrasts. One of the reasons for this phenomenon is that reflections from smooth, black printed areas do not reach the photoconductor.

According to the present invention, a copying apparatus of the above described type is preferred which comprises one or more of the following features: (a) the apparatus has a single electromotor for driving the photoconductor and driving the mirror arrangement, and the two drives are mechanically interconnected with each other; (b) a return spring is provided for retracting the mirror arrangement, as well as a clutch between the drive for the mirror arrangement and the drive of the photoconductor, said clutch being released as soon as the mirror arrangement has passed the end of the scanning path; On both sides of the displaceable mirror arrangement, guide rails are provided which extend in the direction of the line of displacement; (d) the drive for the mirror arrangement and the drive for the photoconductor are connected by an nonextendible rope or band which is guided in a circular disk and is capable of being wound off of and onto the disk. The circular disk is arranged coaxially with the roller or drum carrying the photoconductor, and one end of the rope or band is finnly attached to the circular disk and the other end is firmly attached to the displaceable mirror arrangement. A clutch is provided between the circular disk and the roller or drum.

Further objects, features and advantages of the copying apparatus according to the invention will become apparent from the following description of preferred embodiments of the invention, considered with reference to the figures of the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE PREFERRE EMBODIMENTS Before dealing with the more general teaching of the present invention, reference is made to FIGS. 1a and 1b which illustrate the operation of the apparatus according to the invention by way of a particularly lucid, preferred embodiment of the inventive apparatus.

An original 1, shown as a book, is disposed on a transparent planar support plate 2 which may consist .of, for example, glass. Beneath the support plate two rigidly inter-connected mirrors 3 and 4 are arranged which form an angle of 90 with each other. The line of juncture of mirrors 3 and 4 extends parallel to the support plate 2, and each forms an angle of 45 with the support plate carrying the original. The mirror surfaces of the two mirrors forming an angle with each other face the support. The mirrors are mounted for displacement on rails 5 and 6 which extend parallel to the support plate 2.

Pulleys 17 and 18 are arranged to both sides of the photoconductor drum and coaxially with it. The diameter of these pulleys is one half that of the photoconductor drum. Thus, upon rotation of the pulleys with the photoconductor drum, their circumferential speed equals one half that of the photoconductor drum. The two pulleys 17 and 18 may be selectively connected with and released from the drum by means of a clutch diagrammatically shown by pins 19 and 20, which may be operated magnetically, for instance. Steel bands 21 and 22 are fastened to the pulleys l7 and 18, respectively. The other ends of the steel bands are fastened to the carriage 23 which is displaceable on the rails 5 and In FIGS. la and lb, this carriage is diagrammatically shown as a frame formed by four rods 24, 25, 26, and 27, with the frame being suspended from four wheels 28, 29, 30, and 31. The double mirror 3,4 is also attached to this frame.

With the direction of rotation of the photoconductor drum as shown in the drawings, the steel band 22 must be deflected by a fixed roller 32. Further, the carriage 23 is connected with a return spring 33 which returns it to the dotted initial position when the pins 19 and 20 are released.

In the position of the mirrors 3 and 4 shown by the solid lines in FIG. la, the area 10 at the extreme lefthand side of the original 1 is reproduced through the slot 11 onto a photoconductor 13 which may be rotated by means of a drum 12. This reproduction is done with the aid of mirrors 7 and 8 fixedly mounted in the apparatus and a likewise fixedly mounted lens 9. During operation, the drum 12 carrying the photoconductor 13 is rotated such that the photoconductor 13 moves in the direction of the arrow at a speed v. In this manner, the carriage carrying the mirrors is displaced parallel to the support plate 2 at a speed v/2.

The position shown by the solid lines in FIG. la is the end position of the mirror arrangement. On the other hand, the initial position of the mirrors 3 and 4 is shown by dotted lines. In this initial position the area at the extreme right of the original 1 is reproduced through the slot 11 onto the photoconductor 13. It is apparent that the scanning area moves along the original at a speed v when the mirrors travel at a speed v/2. Furthermore, it can be seen that the opticaldistance from the scanned area to the photoconductor is always constant.

Prior to exposure through the slot 11, the photoconductor 13 .is charged in the normal manner by means of a corona 14, and the latent electrostatic charge pattern formed on the photoconductor by exposure is developed in a developing station 15. In a transfer station 16, the developed image is transferred onto a web of paper 47. In principle, it is also possible to use a charge-transfer process or to employ zinc oxide paper, in which case the apparatus must be constructed so that nonreversed copies are produced by an appropriate number of reversals.

The mirrors 3 and 4 may be of trapezoidal shape, as indicated in the plan view shown in FIG. 1b. The shape of the trapezoid is determined by the aperture angle of lens 9 which is utilized. The trapezoidal mirrors 3 and 4 converge toward the lens 9 at about the same angle as is determined by the lens and the width of the original.

The apparatus according to the present invention is equipped with a special illuminating system. An illuminating mirror 38 is firmly connected with mirrors 3 and 4. For example, it may also be mounted on the carriage 23. As can be seen from both the initial position, shown by dotted lines, and from the end position of the three mirrors, shown by the solid lines, the three mirrors 3, 4, and 38 are firmly combinedto form a single mirror arrangement which may be displaced along the rails extending parallel to the support plate 2. The light rays of a light source 34, preferably an elongated luminous surface, thelongitudinal direction of which extends normal to the plane of the drawing in FIG. 1a and the longitudinal and transverse measurements of which correspond to the proportions of the slot 11 (taking into account, of course, that the light impinges obliquely) are directed through the support plate 2 onto the original 1 by means of lens 35, a fixed return-deflecting mirror 36, and an illuminating mirror 38. The illuminating mirror 38 is arranged at right angles to the support plate 2, and the path of the illuminating rays is selected so that, at the beginning of the scanning process (i.e., in the position shown by the dotted lines in FIG. 1a), the elongated luminous surface 34 illuminates the original exactly in the area corresponding to the image producedby the lens 9 and'the mirrors 8, 7, 4, and 3 on the strip of photoconductor limited by the slot 11. In FIG. la, this is diagrammatically indicated by the intersection 37 of the main scanning direction and the main illuminating direction.

By arranging the mirror 38 vertically to the support plate 2, it is ensured that, by a displacement of the mirror38 to the left-hand'sideat a speed v/2, the main illuminating point 37 likewise travels to the left along the surface of the support plate 2, but at a speed v. The main scanning point also travels to the left at the same speed. In this manner, care is taken that the scanned area, but only the scanned area, is always illuminated. The fact that the illumination is effected at an angle which differs from 90 is highly desirable, because it has been found that by copying substantially outside of the conditions of reflection, copies are produced having a contrast which is much better than when working under conditions of reflection. Of course, when decid-" ing on the dimensions of the elongated luminous surface 34 and on the positions of the lens 35 and the fixed mirror 36, it must be taken into account that the luminous surface 34 is reproduced on a surface 2 which is inclined with respect to the direction of illumination, and the resulting enlargement of the surface must be considered. If desired, the dimensions of the image of the lamp 34 may be changed by means of a cylindrical lens. It is also possible to provide an additional illumination device comprising a second light source 34a a third lens 35a, a second retum-deflection mirror 36a, and a second illuminating mirror 38a.

In the following, the general teaching of the present invention is illustrated with reference to FIG. 2;

In this scanning system, which is asymmetrical, two

surface 2 is scanned at an angle of 90 by a stationary lens The virtual image plane 342 formed by the two mirrors 3 and 4 is shown as a dotted line. The direction in which the mirrors are displaced coincides with the bisector 340 of the angle formed between the plane 2 and the virtual plane 342.

- The virtual plane 32 of the surface 2 reflected by the of the mirror;3=.being the plane of symmetry of the double angle 2a. The second reflection of the plane 2 by the mirror 4 produces the virtual image 3420f the plane. This plane is found by reflecting the angle B mirrors 3 and 4 are provided by means of which the formed between the virtual plane 32 and the plane of the mirror 4 on the other side of the latter plane. Because it is a precondition that the original is to be scanned on the plane 2 at an angle of the direction 90 of the optical axis of the lens 9 is found by drawing a perpendicular line on the virtual image 342 of the plane 2. In the drawing, this is diagrammatically indicated by the right angle 341 in FIG. 2. This right angle corresponds to the right angle 23 at which the plane 2 is scanned.

In the following, it will be described how, with a given arrangement of the plane 2 and a given initial position of the mirrors 3 and 4, the direction of displacement of the mirrors 3 and 4 along a line of displacement 340 is determined:

The position of this straight line is defined in that the virtual image 342 of the plane 2 produced by the two mirrors 3 and 4 is displaced only'within itself, by the displacement of the mirrors 3 and 4 along the line of displacement 340, but is not displaced in the perpendicular direction, i.e. in the direction of the optical axis 90. It is assumed that first the position of thernirror 4 is fixed and that the mirror 3 is moved in the direction of its normal by half the length of the arrow 31. Accordingly, the virtual image 32 is also displaced in the direction of the arrow 31. Because of the second reflection by the mirror 4, the virtual image 342'is displaced by a distance which corresponds to arrow 41. By this displacement, point I of the virtual image 342, for example, is displaced to a position I. Since it is conditioned that a displacement of the virtual image 342 shall take place within its plane only, point I must be moved from its position by an appropriate displacement and assume a position within the plane of the virtual image 342, as indicated by the position 1''. Thus, in order to displace the virtual image 342 without the application of a normal component, i.e. within the virtual image plane, a further displacing component 42 must be provided, which may be achieved by the mirror 4 which initially had been static. By the vectorial addition of the displacements 41 and 42, the point I in the vir tual plane 342 is displaced to the position I and from there returned to the plane of the virtual image 342 to take position I". The direction of this displacing component 42 is determined by the fact that invariably it is only a displacement vertically to the plane of a mirror which causes a displacement of the virtual image. Thus, the component 42 must beat right angles to the plane of the mirror 4, as indicated by the angle 43. The direction of the line of displacement 340 is defined in that the component of displacement vertically to the plane of the mirror 3 must have the length of the arrow 31, and the component of displacement vertically to the plane of the mirror 4 must have'the length of the arrow 42. The direction of the'line of displacement 340 is obtained in that the 'vectors of displacement issuing, for example, from the intersection of mirrors 3 and 4 are marked down, and that at their ends perpendicular lines to the vectors are drawn, and the intersection of these normals is then connected with the intersection 9 of the two mirrors 3 and 4. When the mirrors 3 and 4 are displaced by the length of the vector 34 thus obtained, the mirror 3 is displaced in a vertical direction j by the length of the vector 31 and, at the same time, the mirror 4 is displaced in the vertical direction by the length of the vector 42.

The same method for determiningthe lines of displacement which is described above for two mirrors having one reflection each may also be applied in the case of more than two mirrors and when more than two reflections take place at each mirror.

In the case of a mirror arrangement composed of only two mirrors with only one reflection from each mirror, the direction of the line of displacement is defined as the bisector of the angle formed by the plane of the support plate and the virtual image of the image on the support plate formed by the two mirrors. This angle between the two planes is independent of a rotation of the double mirror and is determined solely by the angle formed by the two mirrors.

The following decisive-advantages are achieved by the electrophotographic copying apparatus according to the invention:

1. A plane supporting surface for the original is provided.

2. Only one moving optical element is used.

3. Scanning is at right angles to the original.

4. The displaceable mirror arrangement is moved at half the speed of the photoconductor surface.

5. The mirror arrangement is only displaced through half the length of the original to be scanned.

6. The height of the apparatus may be maintained relatively small. I

7. Illumination is by a stationary light source, without any additional moving elements.

8. The mirror arrangement is not susceptible to a rotary motion about an axis parallel to the slot at the photoconductor. i

What is claimed is:

1. An electrophotographic copying apparatus, comprising:

A. a photoconductive surface;

B. means for rotating said photoconductive surface;

C. means for uniformly charging said photoconductive surface;

D. a slotted diaphragm arranged in front of the photoconductor and transversely to its direction of movement, through which the photoconductor surface is exposed;

E. a planar transparent support surface for an original image to be copied;

F. optical means for reproducing said original image upon said photoconductive surface, said optical means comprising i. a first stationary lens for directing a scanned image from said original image to said photoconductive surface;

ii. a reflecting arrangement adapted for displacement along a straight line, said arrangement comprising a. at least two scanning reflecting elements rigidly joining with one another in fixed angular relationship, whereby, when said original image is scanned,

a moving visual image isproduced behind said scanning reflecting elements from the view point of said first stationary lens, and

b. at least one illuminating reflecting element rigidly connected to said scanning reflecting elements and arranged at such an angle to said original image supporting surface that a normal to said illuminating reflecting element, a normal to said original image, and said straight line of displacement lie in a single plane, said straight line of displacement being defined such that said moving virtual image is displaced in a direction also lying in said plane when said reflecting arrangement is displaced along said line;

G. a stationary light source;

H. a second stationary lens for receiving a light beam from said light source and projecting said light into said illuminating reflecting element and from said illuminating reflecting element onto said original image, thereby illuminating the original image, and

I. means for displacing said reflecting arrangement along said line of displacement in response to the circumferential speed of said rotating photoconductive surface whereby said original image is scanned.

2. The electrophotographic copying apparatus as defined by claim I, wherein said reflecting element is a mirror arrangement comprising as said scanning reflecting elements at least two scanning mirrors and as said illuminating reflective element at least one illuminating mirror.

3. The electrophotographic copying apparatus as defined byclaim 2, comprising two scanning mirrors and wherein the line of juncture formed by said joined scanning mirrors extends parallel to the plane of said support surface, and wherein said line of displacement bisects the angle formed between said support surface and said moving virtual image.

4. The electrophotographic copying apparatus as defined by claim 3, wherein said two scanning mirrors are joined at a right angle to said support surface.

5. The electrophotographic copying apparatus as defined by claim 3, wherein said two scanning mirrors are joined at a right angle, wherein each of said mirrors is at an angle of 45 with respect to said support surface, and wherein said line of displacement is parallel to said support plate and normal to said line of juncture between said scanning mirrors.

6. The electrophotographic copying apparatus as defined by claim 3, wherein each of said scanning mirrors has a trapezoidal shape converging in the direction of light travel from said support surface to said first stationary lens.

7. The electrophotographic copying apparatus as defined by claim 2, wherein said optical system further comprises at least one further stationary mirror surface optically cooperating with said first stationary lens.

8. The electrophotographic copying apparatus as defined by claim 1, wherein said original image is an original object.

9. The electrophotographic copying apparatus as defined by claim I, wherein said original image is a stationary virtual image of an original object.

10. The electrophotographic copying apparatus as defined by claim 2, wherein said illuminating mirror is inclined with respect to said support surface at an angle whereby said illuminating light beam for the original image travels over said original image at the same speed as said original image is scanned by said scanning mirrors.

11. The electrophotographic copying apparatus as defined by claim 10, wherein said illuminating mirror is arranged in spaced relationship to said scanning mirrors along the direction of said displacement line for.

said mirror arrangement and normal to said line of displacement and wherein said illuminating mirror is at a right angle to said support surface.

12. The electrophotographic copying apparatus as.

defined by claim 1 l, wherein said illuminating mirror is arranged behind said scanning mirrors in said direction nated at an angle between about 30 and 60.

15. The electrophotographic copying apparatus as defined by claim 14, wherein said light source further comprises a return-deflection mirror positioned behind said light source. I

16. The electrophotographic copying apparatus as defined by claim 11, wherein said illuminating mirror is spaced a distance from said scanning mirrors greater than at least one half of the support surface length which is scanned.

17. The electrophotographic copying apparatus as defined by claim 1, further comprising releasable clutch means for rendering said displacing means selec- 18. The electrophotographic. copying apparatus'as defined by claim 2, wherein said means for displacing said mirror arrangement comprises means for returning said arrangement to a starting position after said scanmng.

19. The electrophotographic copying apparatus as defined by claim 18, wherein said returning means comprises a spring member adapted to be tensioned during said scanning and relaxed to cause said return of said mirror arrangement.

20. The electrophotographic copying apparatus as defined by claim 2, wherein said means for displacing said mirror arrangement comprise at least one guide rail arranged on each side of said mirror arrangement in the direction of said line of displacement and a carriage for said arrangement adapted to be guided upon said rails.

21. The electrophotographic copying apparatus as defined by claim 2, wherein said photoconductive surface is carried by a cylindrical drum, said drum having attached coaxially therewith by means of a selectively engageable clutch at least one pulley havinga radius in a proportion to the radius of said drum equal to the ratio between the rotational speed of said photoconductor and the desired displacement speed of said mirror arrangement, and wherein a non-extendable flexible tension member is attached at one end to said pulley and at its other end to said mirror arrangement.

22. An optical system adapted for use in an electrophotographic copying apparatus having a photoconductive surface, a planar transparent support surface for an original image to be copied, a stationary light source and means for illuminating and scanning said original image with light from said source in response to movement of said photoconductive surface, forre- I producing said original image on said photoconduct ve surface, said optical system comprising:

" A. a stationary lens adapted to direct said light beam" from said scanned original image to said photoconv I ductive surface;

B. a reflecting arrangement adapted for displacement along a straight line, said arrangement comprising i. at least two scanning reflecting elements rigidly joining with one another in fixed angular relationship, whereby, when said original image is scanned, a moving virtual image is produced behind said scanning reflective elements from the view point of said first stationary lens, and

' ii. at least one illuminating reflecting element rigidly connected to said scanning reflective elements and arranged at such an angle to said original image supporting surface that a nonnal to said illuminating reflecting element, a normal to said original image and said straight line of displacement lie in a single plane, said straight line of displacement being defined such that said moving virtual image is displaced in a direction also lying in said plane when said reflecting arrangement is displaced along said line;

C. means for displacing said reflecting arrangement along said line of displacement in response to movement of said photoconductive surface.

wherein said reflecting element is a-mirror arrangement comprising as said scanning reflecting elements at least two scanning mirrors and as said illuminating reflective {element at least one illuminating mirror.

24. The optical system as defined by claim 23, comprising two scanning mirrors and wherein the line of juncture formed by said joined scanning mirrors extends parallel to the plane of said support surface, and wherein said line of displacement bisects the angle formed between said support surface and said moving virtual image.

25. The optical system as defined by claim 24, wherein said two scanning mirrors are joined at a right angle to said support surface.

26. The optical system as defined by claim 24, wherein said two scanning mirrors are joined at a right angle, wherein each of said mirrors is at an angle of 45 with respect to said support surface, and wherein said line of displacement is parallel to said support plate and normal to said line of juncture between said scanning mirrors.

27. The optical system as defined by claim 23,

wherein said illuminating mirror is inclined with respect to said support surface at an angle whereby said illuminating light beam for the original image travels over said original image at the same speed as said original image is scanned by said scanning mirrors. 28. The optical system as defined by claim 27, wherein said illuminating mirror is arranged in spaced relationship to said scanning mirrors along the direction of said displacement line for said mirror arrangement and normal to said line of displacement and wherein said illuminating mirror is at a right angle to said support surface.

29. The optical system as defined by claim 28, wherein said illuminating mirror is spaced a distance from said scanning mirrors greater than at least one half of the support surface length which is scanned.

23. The optical system as defined by claim 22,

30. The. optical system as defined by claim 23, wherein said means for displacing said mirror arrangebe d d ment comprise at least one guide rail arranged on each mem adapted to gm 8 upon Sal ml line of displacement and a carriage for said arrangea side of said mirror arrangement in the direction of said 

1. An electrophotographic copying apparatus, comprising: A. a photoconductive surface; B. means for rotating said photoconductive surface; C. means for uniformly charging said photoconductive surface; D. a slotted diaphragm arranged in front of the photoconductor and transversely to its direction of movement, through which the photoconductor surface is exposed; E. a planar transparent support surface for an original image to be copied; F. optical means for reproducing said original image upon said photoconductive surface, said optical means comprising i. a first stationary lens for directing a scanned image from said original image to said photoconductive surface; ii. a reflecting arrangement adapted for displacement along a straight line, said arrangement comprising a. at least two scanning reflecting elEments rigidly joining with one another in fixed angular relationship, whereby, when said original image is scanned, a moving visual image is produced behind said scanning reflecting elements from the view point of said first stationary lens, and b. at least one illuminating reflecting element rigidly connected to said scanning reflecting elements and arranged at such an angle to said original image supporting surface that a normal to said illuminating reflecting element, a normal to said original image, and said straight line of displacement lie in a single plane, said straight line of displacement being defined such that said moving virtual image is displaced in a direction also lying in said plane when said reflecting arrangement is displaced along said line; G. a stationary light source; H. a second stationary lens for receiving a light beam from said light source and projecting said light into said illuminating reflecting element and from said illuminating reflecting element onto said original image, thereby illuminating the original image, and I. means for displacing said reflecting arrangement along said line of displacement in response to the circumferential speed of said rotating photoconductive surface whereby said original image is scanned.
 2. The electrophotographic copying apparatus as defined by claim 1, wherein said reflecting element is a mirror arrangement comprising as said scanning reflecting elements at least two scanning mirrors and as said illuminating reflective element at least one illuminating mirror.
 3. The electrophotographic copying apparatus as defined by claim 2, comprising two scanning mirrors and wherein the line of juncture formed by said joined scanning mirrors extends parallel to the plane of said support surface, and wherein said line of displacement bisects the angle formed between said support surface and said moving virtual image.
 4. The electrophotographic copying apparatus as defined by claim 3, wherein said two scanning mirrors are joined at a right angle to said support surface.
 5. The electrophotographic copying apparatus as defined by claim 3, wherein said two scanning mirrors are joined at a right angle, wherein each of said mirrors is at an angle of 45* with respect to said support surface, and wherein said line of displacement is parallel to said support plate and normal to said line of juncture between said scanning mirrors.
 6. The electrophotographic copying apparatus as defined by claim 3, wherein each of said scanning mirrors has a trapezoidal shape converging in the direction of light travel from said support surface to said first stationary lens.
 7. The electrophotographic copying apparatus as defined by claim 2, wherein said optical system further comprises at least one further stationary mirror surface optically cooperating with said first stationary lens.
 8. The electrophotographic copying apparatus as defined by claim 1, wherein said original image is an original object.
 9. The electrophotographic copying apparatus as defined by claim 1, wherein said original image is a stationary virtual image of an original object.
 10. The electrophotographic copying apparatus as defined by claim 2, wherein said illuminating mirror is inclined with respect to said support surface at an angle whereby said illuminating light beam for the original image travels over said original image at the same speed as said original image is scanned by said scanning mirrors.
 11. The electrophotographic copying apparatus as defined by claim 10, wherein said illuminating mirror is arranged in spaced relationship to said scanning mirrors along the direction of said displacement line for said mirror arrangement and normal to said line of displacement and wherein said illuminating mirror is at a right angle to said support surface.
 12. The electrophotographic copying apparatus as defined by claim 11, wherein said illuminating mirror is arranged behind said scanning mirrors in said direction of displacement.
 13. The electrophotographic copying apparatus as defined by claim 11, wherein said illuminating mirror is arranged ahead of said scanning mirrors in said direction of displacement.
 14. The electrophotographic copying apparatus as defined by claim 11, wherein said stationary light source is positioned so that said original image is illuminated at an angle between about 30* and 60*.
 15. The electrophotographic copying apparatus as defined by claim 14, wherein said light source further comprises a return-deflection mirror positioned behind said light source.
 16. The electrophotographic copying apparatus as defined by claim 11, wherein said illuminating mirror is spaced a distance from said scanning mirrors greater than at least one half of the support surface length which is scanned.
 17. The electrophotographic copying apparatus as defined by claim 1, further comprising releasable clutch means for rendering said displacing means selectively responsive to said circumferential speed of said rotating photoconductor, and wherein said rotating means comprises an electric driving motor.
 18. The electrophotographic copying apparatus as defined by claim 2, wherein said means for displacing said mirror arrangement comprises means for returning said arrangement to a starting position after said scanning.
 19. The electrophotographic copying apparatus as defined by claim 18, wherein said returning means comprises a spring member adapted to be tensioned during said scanning and relaxed to cause said return of said mirror arrangement.
 20. The electrophotographic copying apparatus as defined by claim 2, wherein said means for displacing said mirror arrangement comprise at least one guide rail arranged on each side of said mirror arrangement in the direction of said line of displacement and a carriage for said arrangement adapted to be guided upon said rails.
 21. The electrophotographic copying apparatus as defined by claim 2, wherein said photoconductive surface is carried by a cylindrical drum, said drum having attached coaxially therewith by means of a selectively engageable clutch at least one pulley having a radius in a proportion to the radius of said drum equal to the ratio between the rotational speed of said photoconductor and the desired displacement speed of said mirror arrangement, and wherein a non-extendable flexible tension member is attached at one end to said pulley and at its other end to said mirror arrangement.
 22. An optical system adapted for use in an electrophotographic copying apparatus having a photoconductive surface, a planar transparent support surface for an original image to be copied, a stationary light source and means for illuminating and scanning said original image with light from said source in response to movement of said photoconductive surface, for reproducing said original image on said photoconductive surface, said optical system comprising: A. a stationary lens adapted to direct said light beam from said scanned original image to said photoconductive surface; B. a reflecting arrangement adapted for displacement along a straight line, said arrangement comprising i. at least two scanning reflecting elements rigidly joining with one another in fixed angular relationship, whereby, when said original image is scanned, a moving virtual image is produced behind said scanning reflective elements from the view point of said first stationary lens, and ii. at least one illuminating reflecting element rigidly connected to said scanning reflective elements and arranged at such an angle to said original image supporting surface that a normal to said illuminating reflecting element, a normal to said original image and said straight line of displacement lie in a single plane, said straight line of displacement being defined such that said moving virtual image is displaced in a direction also lying in said plane when said reflecting arrangement is displaceD along said line; C. means for displacing said reflecting arrangement along said line of displacement in response to movement of said photoconductive surface.
 23. The optical system as defined by claim 22, wherein said reflecting element is a mirror arrangement comprising as said scanning reflecting elements at least two scanning mirrors and as said illuminating reflective element at least one illuminating mirror.
 24. The optical system as defined by claim 23, comprising two scanning mirrors and wherein the line of juncture formed by said joined scanning mirrors extends parallel to the plane of said support surface, and wherein said line of displacement bisects the angle formed between said support surface and said moving virtual image.
 25. The optical system as defined by claim 24, wherein said two scanning mirrors are joined at a right angle to said support surface.
 26. The optical system as defined by claim 24, wherein said two scanning mirrors are joined at a right angle, wherein each of said mirrors is at an angle of 45* with respect to said support surface, and wherein said line of displacement is parallel to said support plate and normal to said line of juncture between said scanning mirrors.
 27. The optical system as defined by claim 23, wherein said illuminating mirror is inclined with respect to said support surface at an angle whereby said illuminating light beam for the original image travels over said original image at the same speed as said original image is scanned by said scanning mirrors.
 28. The optical system as defined by claim 27, wherein said illuminating mirror is arranged in spaced relationship to said scanning mirrors along the direction of said displacement line for said mirror arrangement and normal to said line of displacement and wherein said illuminating mirror is at a right angle to said support surface.
 29. The optical system as defined by claim 28, wherein said illuminating mirror is spaced a distance from said scanning mirrors greater than at least one half of the support surface length which is scanned.
 30. The optical system as defined by claim 23, wherein said means for displacing said mirror arrangement comprise at least one guide rail arranged on each side of said mirror arrangement in the direction of said line of displacement and a carriage for said arrangement adapted to be guided upon said rails. 